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Research and Development Laboratories 

of the 
Portland Cement Association 



RESEARCH D! P\KTMI NT 

Bulletin 63 



Hydraulic Pressure in Concrete 



»y 



T. C. Powirs 



April, 1956 
Chicago 



K.-i IV i t! htcd 

the 

! N I v ' Ju 



HYDRAULIC PRESSURE IN CONCRETE 



T.C. Powers 1 



The final report of the Subcommittee on Uplift in Masonry Dams of the 
Committee on Dams^) states that: "The data applicable to the question of 
foundation uplift are held to be adequate to warrant a report on this phase. 
There are numerous unanswered questions and a scarcity of field data as to 
uplift effects in the concrete of the dam structure, and prospects for obtain- 
ing such information in the near future are not very promising. Hence, this 
report is presented as a statement of foundation uplift." The committee's 
avoidance of conclusions pertaining to pore pressure in concrete becomes 
understandable when one examines the various discussions of Mr. L.F. 

Harza's paper. (2) 

During the past 15 years, work in the laboratories of the Portland Cement 
Association produced information concerning the structure of hardened port- 
land cement paste having a direct bearing on the question of hydraulic uplift 
in concrete. In this paper I shall summarize that information. 

This discussion will be restricted to a consideration of hydraulic pressure 
in the pores of concrete; it does not deal specifically with conditions in the 
foundation or at the junction of the dam and foundation. 

Hardened cement paste in a modern concrete dam constitutes 15 to 20 per 
cent of the volume of concrete. Hardened paste is a continuous body extend- 
ing from boundary to boundary of the structure. It envelops aggregate parti- 
cles and air voids, isolating them individually. When water penetrates con- 
crete, it penetrates the paste whether or not it penetrates aggregate particles. 
Hence, if the area factor for cement paste can be established, we will at least 
have found a lower limit for the area factor of the whole concrete. 

Submicroscopic Structure of Hardened Paste 

Hardened cement paste contains an amorphous material called cement gel. 
Within the boundaries of a body of paste, cement gel envelops the residue of 
unhydrated cement and non-gel part of the hydration products, principally 
crystals of calcium hydroxide. Gel may enclose also submicroscopic spaces- 
holes -representing residues of the original water-filled space in fresh paste 

that did not become filled with gel. 

Cement gel is made up of granules so small that they fall in the class of 
sizes called colloidal. The smallness of these granules, together with the 
fact that they are bound together so as to form a porous solid, justifies call- 
ing the principal part of hydrated portland cement, cement gel. 

The density of hardened cement paste depends upon the degree to which 
gel particles fill all available space. In the densest pastes that have so far 
been made, gel has the following physical characteristics: 

1. Manager, Basic Research Section, Portland Cement Association, 
Chicago, 111. 

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1) volumetric porosity, about 25 per cent 

2) surface area of the gel particles, 6.0 million cm 2 /cc of solid, or 14 mil- 
lion in 2 / in 3 , or 4,200 acres/cu.ft. 

3) average specific gravity of the solids in the gel, about 2.44 

4) diameter of the gel particles, about 100 Angstrom units, or four-tenths 
of a millionth of an inch. 2 

The surface area of gel particles, specific gravity, and volumetric porosity 
were measured experimentally. (3) The size of the average gel particle was 
calculated from specific surface of gel, on the assumption that gel is com- 
posed of equal spheres. Recently, electron photomicrographs were obtained 
showing that the particles actually are spheroidal and have an average dia- 
meter very close to that calculated from volume and surface area. 

In cement paste of the kind found in mass concrete, the quantity of gel is 
insufficient to fill all space within the boundaries of hardened paste; some of 
the originally water -filled space remains unfilled. The porosity of paste as 
measured by its capacity for evaporable water usually ranges from 50 per 
cent upwards. We surmise that in such pastes, gel particles tend to be 
packed close together at sites of original cement grains, 3 and that unfilled 
spaces are residues of original interstitial space. In such pastes, gel is a 
three-dimensional network, webs of the net being made up of gel particles 
mostly in a close-pack arrangement. 

Discussion of Area Factor 

As has been brought out by Terzaghi and Leliavsky,( 4 ) the area factor 
depends upon the nature of the ultimate particles. Ultimate particles are 
those parts of a porous, granular solid that water is unable to penetrate. In 
hardened cement paste, gel particles are the ultimate particles so far as hydro- 
static effects are concerned; they present the surfaces with which water 
makes contact. At least two kinds of observation show that gel particles are 
the ultimate particles: (1) When water vapor is allowed to penetrate dry, 
hardened paste, some of it is adsorbed. After the amount adsorbed was mea- 
sured the surface area of solids reached by water molecules was calcu- 
lated. (3) From surface area, average size could be calculated, assuming 
equal spheres. The calculated average size agreed with the size revealed by 
the electron microscope, as already mentioned. (2) Direct measurements 
show that cement gel is permeable to water. Water flows through the exceed- 
ingly small interstitial spaces— we call them gel pores. 

On the basis of information just summarized, the structure of concrete 
may be visualized as follows: every particle of aggregate and every air void 
in hardened concrete is embedded in a mass of exceedingly small spheroids. 
The spheroids average about a half millionth of an inch in diameter. They 
are packed together to various degrees, the maximum degree giving intersti- 
tial space of about 25 per cent. Water can penetrate the interstitial spaces 
among these particles and can transmit hydraulic force in a normal manner, 
so far as we know. 



2. This is a revision of an earlier published estimate of 140 A. 

3. It should be understood that in the process of hydration the constituents of 
the original cement grains go into solution and that the new product, that 
which we have been discussing, is precipitated from solution. Only a 
small part of the original cement, a residue of the coarsest grains, sur- 
vives if the conditions necessary for hydration are maintained long enough. 



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If gel particles in hardened paste were not attached to each other, that is, 
if they were only packed together as are particles in a bed of sand, the entire 
surface of each particle could be wetted. However, the ultimate particles in 
hardened cement paste are not discrete. They are connected to each other by 
bonded regions that water cannot penetrate. If gel particles were discrete, 
penetration of water into dry concrete would not merely cause a slight swell- 
ing, as it does, but it would also cause the gel to peptize. In other words, 
water would free gel particles from each other and the mass would lose us 
solidity. Water might even be able to disperse the material of which gel par- 
ticles are composed, forming a true solution. Some gels can be readily de- 
stroyed by water as, for example, gels made of caustic alkali and silica, as 
found in concretes affected by the alkali -aggregate reaction. 

Cement gel fails to peptize or dissolve because gel particles are linked by 
chemical bonds. The area thus bonded cannot be wetted and consequently can 
not be subjected to hydraulic pressure. 

Knowing something of the ize and arrangement of gel parti* les we can 
estimate a possible area factor for cement gel when it is subjected to hydrau- 
lic pressure. Let us assume that particles are sphen< al and packed s< is to 
have a porosity of 25 per cent. It is rea nable to assume further that the 
maximum number of points of contact is about 12 per particle. Therefore, 
each sphere might be bonded to its neighbors at 12 spots. A bond consists < 
a linkage between two atoms— a merging of force fields. The area of each 
spot can then »re be estimated from the radius oi he bonded a' data on 
atomic radii being available. With area per bond estimated, w» ieed only to 
multiply by number oi bonds per particle to find total b< ded area per p. tlcls 

It works out that if each of the particles is bonded at 12 points by single 
pans of atoms, 0.2 per rent of the part le area Is bonded, leaving 99.8 per 
•nt of the area a< essible to water. Thus the wettable | rea fraction of gel 
particles might be very close to unity, but it would be definitely less than 
unity. 

The foregoing di ussion does no more than arrive at an estimate of a 
possible upper limit of the area factor. The actual area factor i obtainable 
only by experiment. 

The latest values of area factors for concrete are those published recenth 
by Serafim. (^ Following Mc Henry's^) suggestion, Serafim estimated area 
factors (boundary porosity) by non -destructive tests, that is, by stress-strain 
measurements. Specimens were dried and then subj* ed to nitrogen pres- 
sure in such a way as to produce tension in the middle section of a < nder 
by outflow through the ends. Some of the specimens were tested in the satu- 
rated state with water, as well as with nitrogen. Serafim s pnncipa Malta 
are given in Table I. 

Note that the factors obtained with nitrogen are like those obtained by 
Leliavsky and others in previous experiments, they range from .83 to .99 
among the various grades of concrete. In some tests on specimens dried at 
105° C, data not shown in Table I, factors not significantly different from unity 
were obtained. These results may have been Influenced by internal cracks 
produ d during drying. 

Area i rs obtained from water percolation are distinctly smaller than 
those obtained with nitrogen. The discrepancy between the two sets of re- 
sults was explained by Serafim in terms of mmobtlity (assumed) of adsorbed 
water molecules. This explanation, though possibly correct seems doubtful 
on the basis of other considerations pertaining to the adsorbed state. 

742-3 



TABLE I. 

Area Factors as Determined by Serafim 



Water-Cement Area Factor as Measured With : 
Kei. no. Ra tio by Weight Nitrogen water 



3 0.72 0.90 

8 0.72 .95 .74 

1 0.68 .86 

2 0.66 .86 

4 0.60 .83 

9 0.60 .89 .69 

5 0.55 .85 

10 0.35 -85 -42 

11 0.35 -93 .A4 
7 0.30 .99* 

12 0.30 .85 .^3 



* High value might be related to cracks produced during 
drying . 

Both sets of data show that for water -cement ratios within the range 
practical for concrete dams, the area factor is a large fraction of the total 
area. With the possible exception of the three lowest values obtained with 
water, these factors obtained by Serafim seem compatible with what is now 
known about the structure of hardened portland cement paste. 

Discussion of Intensity Factor 

It is pertinent to inquire into conditions under which hydrostatic pressure 
can develop in the interior of concrete. For the most part the discussion 
will exclude considerations of seepage along construction planes, structural 
cracks, and other imperfections, though such seepage is obviously of practi- 
cal importance. The purpose is to call attention to significant characteristics 
of concrete that do not seem to be generally known. 

The same studies of physical properties of hardened cement paste already 
referred to account for the fact that concrete, especially mass concrete, is 
seldom if ever saturated at the time it goes into service and that in most of 
the structure it may never become saturated. In general, negative rather 

positive hydrostatic pressures prevail. 

Since negative hydrostatic pressure may be an unfamiliar concept, the 
following remarks are offered to indicate what the term is intended to signify. 
In general, when we observe water flowing in any sort of conduit, we under- 
stand that flow occurs because of a difference in hydraulic pressure. Simi- 
larly, capillary rise indicates that a meniscus has produced a pressure dif- 
ference, and if pressure at the base is called zero, pressure under the menis- 
cus is negative. If capillary rise exceeds 33 ft. as it does in tall trees, the 
liquid actually is in tension. 4 When water is adsorbed by dry concrete, inward 

4. An interesting short article on hydrostatic tension in liquids may be found 
in the Scientific Monthly , 58, 415, June 1949. 

742-4 



flow continues as long as hydrostatic pressure inside remains negative 
with respect to zero pressure outside. In this case, adsorption is due mostly 
to the spread of water over enormous, internal surface areas (about 12,000 
acres per cu. yd. of concrete) rather than to meniscuses, but the effect is the 

same. 

The magnitude of negative pressure is an unsaturated region in concrete 

relative to zero pressure in a saturated region is a function of the degree of 
saturation of cement paste in the unsaturated region. It is a maximum when 
paste in the dry region is bone dry and zero when hardened paste is satu- 
rated. Thus, potential negative pressure are produced whenever pores in 
hardened paste become empty or partly empty. This is the usual condition. 
Even if concrete is sealed so that it can lose no water by evaporation, the 
chemical process of cement hydration reduces volume of water faster than 
solid volume increases and leaves originally water-filled space partly empty. 
This process has been called self -desiccation , w) 

The amount of water withdrawn from pores by self -desiccation is a func- 
tion of degree of hydration of the cement. The amount of water withdrawn 
from pores is equal to about 28 per cent of the amount of water that becomes 
chemically combined. After a prolonged period of hydration, the amount of 
chemically combined water will be about 22 per cent of the weight of cement. 
Twenty-eight per cent of this is 6.2 per cent. Hence, for concrete containing 
376 lb. of cement per cu. yd., the amount of water withdrawn from pores will 
be 0.062 x 376 = 23.3 lb. per cu. yd., or 2.8 gal. per cu. yd. of concrete. This 
is the amount of water that would have to be added to concrete to keep it sat- 
urated. Ordinarily, concrete does not receive anywhere near this amount 
from ordinary curing procedures. Moreover, it generally loses some water 
evaporation during construction. Hence, it is fair to estimate that within two 
or three months after concrete is made, each cubic yard of mass concrete 
will be short about three gallons of water for saturation. As long as this con- 
dition prevails, hydrostatic pressures in the interior of concrete are negative. 

The period required for concrete in a dam to acquire water needed for 
saturation may be a very long time, as may be verified by computations based 
on measured permeability of mass concrete. In certain regions of a dam, 
specifically regions above tailwater level, a saturated condition may never be 
attained, except perhaps in the vicinity of leaky fill planes or structural 

cracks that serve as conduits. 

Experiments described by Carlson and Davis ^ demonstrate the difficulty 
of producing positive pressures under conditions where evaporation can oc- 
cur at the downstream face. In one of Carlson and Davis' experiments a 6- in. 
cylinder 96 inches long was exposed to hydrostatic pressure of 100 lb/in 2 at 
one end and to air maintained at 50 per cent relative humidity at the other. 
Arrangements were made to prevent water from passing the boundaries of 
the specimen except at ends. Bourdon gages were installed at various sta- 
tions along the length of the specimen, one of them being only 4 in. from the 

upstream face. 

In the early stages of the experiment small positive pressures were ob- 
served at stations closest to the upstream face. Within seven years every 
gage, including that 4 in. from the face, registered zero. The gages were in- 
capable of registering negative pressures that must have existed. 

The magnitude of negative pressure can be calculated by means of the 
relative humidity maintained by free water in concrete. Calculation involves 
the well known equation of Lord Kelvin that relates differences in free energy 
to differences in vapor pressure. It can be shown, for example, that if 

742-5 



humidity inside concrete at the exposed face is kept by evaporation at 50 per 
cent, hydrostatic pressure is about -14,000 lb/in 2 . Hence, in the Carlson and 
Davis experiment if the downstream end of the test specimen was kept at that 
degree of dryness, hydrostatic pressure at the downstream end relative to 
pressure at the nearest point upstream where paste was saturated would be 
about -14,000 ib/in 2 . Between the point where the concrete is just saturated 
and the upstream face, pressure would be positive, rising from zero to 
100 lb/in 2 on a straight-line gradient. Therefore, total pressure drop from 
the upstream to downstream face would be about 

100 - (-14,000) = 14,100 lb/in 2 . 

Computation on a simplified basis indicates that with 100 lb/ in 2 positive 
pressure on the upstream face the pressure would drop to zero at a point 
downstream only 0.7 in. from the face. The fact that a gage 4 in. away from 
the face registered zero, indicating either zero or negative pressure, shows 
that this computation was not far wrong. If the experiment had continued long 
enough to establish a steady state, rate of flow through the specimen would 
have remained practically unchanged if pressure at the upstream face had 
been reduced to zero, merely keeping the upstream face wet. 

Because of development of negative pressure when concrete is subject to 
drying, we should expect negative internal pressures in a concrete dam in all 
parts where the downstream face is dry all or most of the time. At points 
below tailwater level, however, where evaporation from the downstream face 
cannot occur, development of positive hydrostatic pressure is only a matter 

of time 5 . 

Since the concrete above tailwater level tends to remain or to become dry 
by the process just described, water in concrete below tailwater level will in 
time be driven upward under the combined effect of positive pressure in the 
lower part and negative pressure in the upper part. However, as indicated by 
the Carlson and Davis experiment, positive pressure is likely to play only a 
small part in determining the final result, which means that positive pres- 
sures cannot be developed very far above tailwater level or away from the 
front face. 

Hence, in an ideal, flawless concrete dam, we should expect a long period 
of slow change in moisture distribution, the period probably extending over 
many years. Finally, a practically steady state should be reached wherein 
positive pressures in concrete are found near the upstream face and near the 
tailwater level. In the rest of the structure, concrete should remain unsatu; 
rated and hydrostatic pressures should be negative. Variations from the pat- 
tern for a flawless structure will, of course, be produced by cracks, leaky 
fill planes, or perhaps by operation of spillways. 

REFERENCES 

1. Final Report of the Subcommittee on Uplift in Masonry Dams of the Com- 
mittee on Masonry Dams, A.S.C.E. Separate No. 133, 1952. 

2. L.F. Harza, "The Significance of Pore Pressure in Hydraulic Structures." 
Trans. A.S.C.E. 114, 193 (1949). 



5. It is doubtless unnecessary to call attention to the fact that negative pres- 
sures in the water films are fully balanced within the structure and there- 
fore do not contribute to uplift forces produced in regions where the 

hydrostatic pressure is positive. 

742-6 



3. T.C. Powers and T.L. Brownyard, "Studies of the Physical Properties of 
Hardened Portland Cement Paste," Part 3. Proc. Am. Concrete Inst. 43, 
487-491 (1946); PCA Bulletin 22. 

4. Serge Leliavsky Bey. Discussion of Ref. 1. Trans. A.S.C.E. 114 , 230 
(1949). 

5. T.C. Powers, "A Discussion of Cement Hydration in Relation to the Curing 
of Concrete." Proc. Highway Research Board 27, 178 (1947); PCA Bulletin 
25. 

6. R.W, Carlson and R.E. Davis. Discussion of Ref. 1. Proc. A.S.C.E. 74, 
1532 (1948). 

7. J. Laginha Serafim, "Uplift Pressure in Concrete Dams." Laboratdrio 
Nacional de Engenharia Civil, Pub. 55, Lisbon, 1954. (In Portuguese) 

8. D. Mc Henry, "The Effect of Uplift Pressure on the Shearing Strength of 
Concrete." Trans, m Congress Large Dams, Vol. I, Rep. 48, Estocolmo, 
1948. 



742-7 



Bulletins Published by the 

Research Department 

Research and Development Division 

of the 
Portland Cement Association 



Bulletin 1 



Bulletin 2 



Bulletin 



Bulletin 



Bulletin 



i< 



Bulletin 5A 



"Estimation of Phase Composition of Clinker in the System 3CaO 
Si02-2Ca0 SiOj-3CaO Al,0 3 -4Ca0 AI.O3 Fe>0 3 at Clinkering Temper- 
atures," by L. A. Dahl, May, 1939. 

Reprinted from Rock Products, 41, No. 9, 48; No. 10. 4<>; No. 11. 42; No. 12, 44 
(1938); 42. No. 1, 68; No. 2. 4G; No. 4. 50 (1939). 

"The Bleeding of Portland Cement Paste, Mortar and Concrete Treated 
as a Special Case of Sedimentation, " by T. C. Powers; with an appendix 
by L. A. Dahl; July, 19:19. 

"Rate of Sedimentation: I. Nonflocculated Suspensions of Uniform 
Spheres; II. Suspensions of Uniform-Size Angular Particles; 111. 
Concentrated Flocculated Suspensions of Powders"; by Harold H 
Steinour, October, 1944. 

Reprinted from Industrial and Engineering Chemistry, U>. 618. 840, 901 (1944). 

"Further Studies of the Bleeding of Portland Cement Paste," by Harold 
H. Steinour, December, 1045. 

A Working Hypothesis for Further Studies of Frost Resistance of 
Concrete," by T. C. Powers. February, 1945. 

Reprinted from Journal of the American Conrrett Instil I I ebruary, 1 ( .»45); Pro- 
ceedings, 41. 24'j (l'Uo). 

Supplement to Bulletin 5; Discussion of the paper "A Working Hy- 
pothesis for Further Studies of Frost Resistance of Concrete," by 

T. C. Powers; discussion by: Ruth D. Terzaghi, Douglas McIIenrv and 
H. W. Brewer, A. R. Collins, and Authoi : March, 1946. 

Reprints) from Jov ./ of the A ican Concrete Institute Supplement ( Nov< tuber 
1945); Proceedings, A\, 272-1 (1945). 

Dynamic Testing of Pavements," by Gerald Pickett, April, 1945. 

Reprinted frotn Journal of the American Concrete Institute (April, 1945); Proceed- 
ings, 41, 473 (1945 

Equations for Computing Elastic Constants from Flexural and Tor- 
sional Resonant Frequencies of Vibration of Prisms and Cylinders," 

by Gerald Pickett, September, 1945. 

Reprinted from Proceedings. American Society for Testing Materials, 45, 846 (1945 
discussion 

Flexural Vibration of Unrestrained Cylinders and Disks," by Gerald 
Pickett, December, 1945. 

Reprinted from Journal of Applied P> s. 16, 820 (1945). 

"Should Portland Cement Be Dispersed?" bv T. C. Powers, February, 
1946. 

Reprinted from Journal ofthe Aim in Concrete Institute (November , 1945); Pr 
ceedings, 42, 117 (1946). 

Bulletin 10— "Interpretation of Phase Diagrams of Ternary Systems," by L. V Dahl, 

March, 1946. 

Reprinted from J nalofPl calCltet 50,96(1946). 



Bulletin 



it 



Bulletin 7 



• i 



Bulletin 8 



44 



Bulletin 9 



Bulletin 1 1 



a 



Shrinkage Stresses in Concrete: Part 1 — Shrinkage or Swelling , 
Its Effect upon Displacements and Stresses in Slabs and Beams of 
Homogeneous, Isotropic, Elastic Material; Part 2 — Application of the 
Theory Presented in Part 1 to Experimental Results"; by Gerald 
Pr< K.ETT, March, 19 16. 

Reprinted from Journal ofth> \ merican Concrete Institute (January and Februar; 
L946); Pro> lino 42,165.361 1946). 



15 



Bulletin 12 



1 1 



Bulletin 1 



Bulletin 



Bulletin 15 



l 4 



Bulletin 



Bulletin 17 



Bulletin 18 



Bulletin 19 



Bulletin 



Bulletin 21 



Bulletin 22 



Bulletin 23 



Bulletin 



Bulletin 



The Influence of Gypsum on the Hydration and Properties of Portland 
Cement Pastes," by William Lerch, March, 194(3. 

Reprinted from Proceedings, American Society forTesting Materials, 46, 1251 (1946). 

"Tests of Concretes Containing Air- Entraining Portland Cements or 
Air- Entraining Materials Added to Batch at Mixer," by H. F. Gonner- 

man, April, 1947 

Reprinted from Journal of the American Conen Institute (June, 1944> ; Proceedings. 
40, 477 (1944); al-«- supplementary data and analysis, reprinted from Supplement 
(November, 1944 I; Proceedings, 40, .*)08-l (1944). 

"An Explanation of the Titration Values Obtained in the Merriman 
Sugar-Solubility Test for Portland Cement," by William Lerch, 
March, 1947. 

Reprinted from AST M Bulletin, No. 145, (>2 (March, 1947). 

The Camera Lucida Method for Measuring Air Voids in Hardened 
Concrete," by George J. Verbeck, May, 1947. 

Reprinted from Journal of the American Concrete Institute (May, 1047); Proceed- 
in,/,. 43, 1025 (1947). 

"Development and Study of Apparatus and Methods for the Determina- 
tion of the Air Content of Fresh Concrete," by Carl A Mbnzel, May, 
1947. 

Reprinted from Journal of the American Concrete Institute (Ma\ 1947); Proceed- 
ings, 43. 1053 (1947). 

"The Problem of Proportioning Portland Cement Raw Mixtures: 
p art i_a General View of the Problem; Part II— Mathematical Study 
of the Problem; Part HI— Application to Typical Processes; Part IV— 
Direct Control of Potential Composition"; by L. A. Dahl, June, 194/. 

Reprinted from Rock Products, 50, No. 1, 109; No. 2, 107; No. 3, 92; No. 4, 122. 
(1947). 

"The System CaO-Si0 2 -H,0 and the Hydration of the Calcium Sili- 
cates, " by Harold M. Steinour, June, 1947. 

Reprinted from Chemical Reviews. 40, 391 (1947). 

"Procedures for Determining the Air Content of Freshly-Mixed Con- 
crete by the Rolling and Pressure Methods," by Carl A Menzel, 
June, 1947. 

Reprinted from Proceedings, American Soci*' >t for Testing Materials, 47, 833 (1947). 

"The Effect of Change in Moisture-Content on the Creep of Concrete 
under a Sustained Load," bv Gerald Pickett, July, 1947. 

Reprinted from Journal of the Am* an Concrete Institute (February, 1942); Pro- 
ceedings, 38, 333 (194 J . 

Effect of Gypsum Content and Other Factors on Shrinkage of Concrete 
Prisms," by Gerald Pickett, October, 1947. 

Reprinted from Journal of the American Concrete Institute (October. 1947.; Pro- 
ceedings, 44, 149 (1948). 

"Studies of the Physical Properties of Hardened Portland Cement 
Paste," by T. C. Powers and T. L. Brownyarp, March, 1948. 

Reprinted from Journal of the American Concrete Institute (totober- Dumber. 
194t',; January-April. 19 17): Proceedings, 43, 101. 249. 409, o49, 669, 84o. 933 
.19471. 

"Effect of Carbon Black and Black Iron Oxide on Air Content and Dura- 
bility of Concrete," by Thomas G. Taylor, May, 1948. 

Reprinted from Journal of the Am. an ConrreU Institute ( April. 1948); Proceed- 
inga, 44, 013 (1948). 

"Effect of Entrained Air on Concretes Made with So-Called 'Sand- 
Gravel' Aggregates," by Pail Klieger, November, 1948. 

Reprinted from Journal of the American Concrete Institute (October. 1948); Pro- 
ceedings, 45, 149 (1949). 

"A Discussion of Cement Hydration in Relation to the Curing of Con- 
crete," by T. C. Powers, August, 1948. 

Reprinted from Proceedings of the Highway Research Board, 27, 178 (1947). 

16 



k i 



* 1 



Bulletin 26— "Long-Time Study of Cement Performance in Concrete. This bulletin 

comprises four installments of the report of this investigation, by K K. 
McMillan, I. L. Tyler, W. C. Hansen, William Lerch, C. L. Ford, and 
L. S. Brown, August, 1948. 

Reprinted from Journal of the Anuricau Concrete Institute (February- May. 1948); 
Proceedings, 44, 441. 553. 743. 877 (1948). 

Bulletin 27— "Determination of the Air Content of Mortars by the Pressure Method, 

by Thomas G. Taylor, February, 1949. 

Reprinted from ASTM Bulletin, No. 155, 44 (December. 1948). 

Bulletin 28 — "A Polarographic Method for the Direct Determination of Aluminum 

Oxide in Portland Cement," by C. L. Ford and Lorrayne Le Mar, 
April, 1949. 

Reprinted from ASTM Bulletin. No. 157, 66 (March, 1949). 

Bulletin 29 — "The Nonevaporable Water Content of Hardened Portland-Cement 

Paste — Its Significance for Concrete Research and Its Methods of 
Determination," by T. C. Powers, June, 1949. 

Reprinted from ASTM Bulletin, No 158, 68 (May, 1949). 

Bulletin 30 — "Long-Time Study of Cement Performance in Concrete — Chapter 5. 

Concrete Exposed to Sulfate Soils," by F. R. McMillan, T. E. Stanton 
I. L. Tyler and \\ . C. Hansen, Derember, 1949. 

Reprinted from a Special Publication of the American Concrete Institute (1949). 

Bulletin 31 — "Studies of Some Methods of Avoiding the Expansion and Pattern 

Cracking Associated with the Alkali- Aggregate Reaction," by William 

Lerch, February. 1950. 

Reprinted from Special Technical Publication No. 99. published by American Soci- 
ety for Testing Materials (1950). 

Bulletin 32— "Long-Time Study of Cement Performance in Concrete — Chapter 6. 

The Heats of Hydration of the Cements," by George J. \ erbeck and 
Cecil W. Foster, October, 1949. 

Reprinted from Proceedings, American Society for Testing Materials, 50, 1235 
(1950 

Bulletin 33— "The Air Requirement of Frost-Resistant Concrete," by T. C. Powers; 

discussion bv T. F A\ illis. 

Reprinted from Proceedings of the Highway Research Board, 29, 184 (1949). 

Bulletin 34 — "Aqueous Cementitious Systems Containing Lime and Alumina," 

by Harold H. Steixqur, February, 1951. 

Bulletin 35 — "Linear Traverse Technique for Measurement of Air in Hardened 

Concrete/' by L. S. Brown and C. U. Pierson, February, 1951. 

Reprinted from Journal of the American Concrete Institute (October, 1950); P 
ceedings, 47, 117 (1951). 

Bulletin 36— "Soniscope Tests Concrete Structures/* by E. A. Wftitehurst, February 

1951 

Reprinted from Journal of t fie American Concrete Institute (February, 1951); Pro- 
ceedings, 47, 433 1951). 

Bulletin 37 — 'Dilatometer Method for Determination of Thermal Coefficient of 

Expansion of Fine and Coarse Aggregate," by George J Verbe<r and 
Werner E. Hass, September, 1951. 

Reprinted from Proceedings of the Highway Research Board. 30, 187 (195 IK 

Bulletin 38 — "Long-Time Study of Cement Performance in Concrete — Chapter 7. 

New York Test Road/' by F. H. Jackson and L L. Tyler, October, 1951. 

Reprinted from Journal of the American Concrete Institute (June, 1951 I ; Proceedings 
47, 773 (1951). 

Bulletin 39 — "Changes in Characteristics of Portland Cement as Exhibited by Lab- 
oratory Tests Over the Period 1904 to 1950," by H. F. Gonnerman and 

William Lerch. 

Reprinted from Special Publication \'o. 127 published by American Society for 
Testing Materials. 

17 



Bulletin 40 — "Studies of the Effect of Entrained Air on the Strength and Dura- 
bility of Concretes Made with Various Maximum Sizes of Aggregate,' * 

by Paul Klieger. 

Reprinted from Proceedings of the Highway Research Board, 31, 177 (1952). 



Bulletin 41 



Bulletin 42 



Bulletin 



Bulletin 



Bulletin 



Bulletin 



'Effect of Settlement of Concrete on Results of Pull-Out Bond Tests," 

by Carl A, Menzel, November, 1952. 

"An Investigation of Bond Anchorage and Related Factors in Rein- 
forced Concrete Beams," by Carl A. Menzel and William M. Woods, 
November, 1952, 

"Ten Year Report on the Long-Time Study of Cement Performance 
in Concrete," by Advisory Committee of the Long-Time Study of Cement 
Performance in Concrete, R. F. Blanks, Chairman, 

Reprinted from Journal of the American Concrete Institute (March, 1953); Proceed- 
ings, 49, 601 (1953). 

"The Reactions and Thermochemistry of Cement Hydration at Ordi- 
nary Temperature," by Harold H. Steinour, 

Reprinted from Third International Symposium on the Chemistry of Cement. Lon- 
don. Sept. 1952. 

"Investigations of the Hydration Expansion Characteristics of Portland 
Cement," by H. F. Gonnerman, Wm. Lerch, and Thomas M. Whiteside, 
June, 1953, 

"Theory of Volume Changes in Hardened Portland Cement Paste 
During Freezing," by T. C. Powers and R. A. Helmuth. 

Reprinted from Proceedings of the Highway Research Board, 32, 285 (1953). 



Bulletin 47 — "The Determination of Non-Evaporable Water in Hardened Portland 

Cement Paste," by L. E. Copeland and John C. Hayes. 

Reprinted from ASTM Bulletin No. 194, 70 (December, 1953). 

Bulletin 



"The Heats of Hydration of Tricalcium Silicate and beta-Dicalcium 
Silicate," by Stephen Brunauer, J. C. Hayes and W. E. Hass. 

Reprinted from Journal of Physical Chemistry, 58, 279 (1954). 



Bulletin 



Bulletin 49A 



"Void Spacing as a Basis for Producing Air-Entrained Concrete, T 

by T. C. Powers. 

Reprinted from Journal of the American Concrete Institute (May, 1954); Proceed- 
ings, 50, 741 (1954). 

—Discussion of the paper "Void Spacing as a Basis for Producing Air- 
Entrained Concrete," by J. E. Backstrom, R. W. Burrows, V. E. Wolk- 
odoff and Author, T. C, Powers. 

Reprinted from Journal of the American Concrete Institute (Dec, Part 2, 1954); Pro- 
ceedings, 50, 760-1 (1954). 

Bulletin 50— "The Hydrates of Magnesium Perchlorate," by L, E. Copeland and R. 

H. Bragg. 

Reprinted from Journal of Physical Chemistry, 58, 1075 (1954). 



Bulletin 51 



Bulletin 



Bulletin 



Bulletin 



"Determination of Sodium and Potassium Oxides in Portland Cement 
Raw Materials and Mixtures, and Similar Silicates by Flame Photom- 
etry," by C. L. Ford. 

Reprinted from Analytical Chemistry, 46, 1578 (1954). 

"Self Desiccation in Portland Cement Pastes," by L. E. Copeland and 
R. H. Bragg. 

Reprinted from ASTM Bulletin, No. 204, 34 (February, 1955). 

"Permeability of Portland Cement Pastes," by T. C. Powers, L. E. Cope- 
land, J. C. Hayes and H. M. Mann. 

Reprinted from Journal of the American Concrete Institute, (November, 1954) ; Pro- 
ceedings, 51, 285 (1955). 

4 'Some Observations on the Mechanics of Alkali- Aggregate Reaction,' * 

by L. S. Brown. 

Reprinted from ASTM Bulletin, No. 205, 40 (April, 1955). 

18 



56— 



Bulletin 57 



55— -An Interpretation of Published Researches on the Alkali- Ag&regat- 
Ruction • Part 1-The Chemical Reacti-ns and Mechanism of Expans 
fion Part ™A Hypothesis Concerning Safe and Unsafe Reactione 
wkh Reactive Silica in Concrete," by T. C. Powers and H. H. Steinoub 

Reprinted from Journal of the American Concrete Intitule (February and April. 
1955); Proceedings, 51, pp. 497 and 785 (19o5). 

Comparison of Results of Three Methods for Determining Young's 
Modulus of Elasticity of Concrete/' by R. E. Philleo. 

Reprinted from Journal of the American Concrete Institute (January. 19o5) ; Pro- 
ceedings, 51, 461 (1955). 

Osmotic Studies and Hypothesis Concerning Alkali- Aggregate Reac- 
tion," by George J. Verbeck and Charles Gramlich. 

Reprinted from Proceedings, American Society for Testing Materials, 55, (19oo). 

Bulletin 58-"Basic Considerations Pertaining to Freezing and Thawing Tests," 

bv T. C. Powers. „ x cc mq ... 

Reprinted from Proceedings, American Society for Testing Materials, 55, (19oo). 

Bulletin 59-"New Study on Reactions in Burning Cement Raw Materials," by L. A. 

Reprinted from Rock Products, 58, No. 5, p. 71; No. 6, p. 102; No. 7. p. 78 (1955). 

Dlll , fl ,. . ft i<i nil (j.Time Studv of Cement Performance in Concrete. Chapter 9. 

Bulletin 60- Long June Study^^ rf T ^V. 6 W^£2r£ 

Under Natural Freezing and Thawing Conditions," by F. H. Jackson. 

Reprinted from Journal of the American Concrete Institute (October, 1955); Pro- 
ceedings. 52, 159 (1955). 

Bulletin 61— "A Method for the Determination of the Cement Content of Plastic 

Concrete," bv W. G. Hime and R. A. Wilms. 

Reprinted from ASTM Bulletin No. 209, 37 (October, 1955). 

Bulletin 62-"Investi£ation of the Franke Method of Determining Free Calcium 
Bulletin 02 ^^7^ and Free Calcium Oxide," by E. E. Pressler, Stephen :Bruxauer 

and D. L. Kantro. 

Reprinted from Analytical Chemistry. Vol.00, p. 00. 1956. 



Bulletin 63— "Hydraulic Pressure in Concrete," by T. C. Powers. 

Reprinted from Proceedings. American Society of Civil Engineers. 81. 742 (July. 1955)